During the 1970's and 1980's, the defense industry encouraged and developed an interconnecting network of computers as a back up for transmitting data and messages in the event that established traditional methods of communication fails. University mainframe computers were networked in the original configurations, with many other sources being added as computers became cheaper and more prevalent. With a loose interconnection of computers hardwired or telephonically connected across the country, the defense experts reasoned that many alternative paths for message transmission would exist at any given time. In the event that one message path was lost, an alternative message path could be established and utilized in its place. Hence, it was the organized and non-centralized qualities of this communications system which made it appealing to the military as a backup communication medium. If any one computer or set of computers was attacked or disconnected, many other alternative paths could eventually be found and established.
This interconnection of computers has since been developed by universities and businesses into a worldwide network that is presently known as the Internet. The Internet, as configured today, is a publicly accessible digital data transmission network which is primarily composed of terrestrial communications facilities. Access to this worldwide network is relatively low cost and hence, it has become increasingly popular for such tasks as electronic mailing and weather page browsing. Both such functions are badge or file transfer oriented. Electronic mail, for instance, allows a user to compose a letter and transmit it over the Internet to an electronic destination. For Internet transfers, it is relatively unimportant how long each file transfer takes as long as it is reasonable. Messages are routed, through no fixed path but rather, through various interconnected computers until they reached their destination. During heavy message low periods, messages will be held at various internal network computers until the pathways cleared for new traditions. Accordingly Internet transmissions are effective, but cannot be relied upon for time high incentive applications.
Web pages are collections of data including text, audio, video, and interlaced computer programs. Each web page has a specific electronic site destination which is accessed through a device known as a web server, and can be accessed by anyone through via Internet. Web page browsing allows a person to inspect the contents of a web page on a remote server to glean various information contained therein, including for instance product data, company backgrounds, and other such information which can be digitized. The remote server data is access by a local browser, and the information is displayed as text, graphics, audio, and video.
The web browsing process, therefore, is a two-way data communication between the browsing user, who has a specific electronic address or destination, and the web page, which also has a specific electronic destination. In this mode of operation, as opposed to electronic mail functions, responsiveness of the network is paramount since the user expects a quick response to each digital request. As such, each browsing user establishes a two-way data communication, which ties up an entire segment of bandwidth on the Internet system.
Recent developments on the Internet include telephone, video phone, conferencing and broadcasting applications. Each of these technologies places a similar real-time demand on the Internet. Real-time Internet communication involves a constant two-way throughput of data between the users, and the data must be received by each user nearly immediately after its transmission by the other user. However, the original design of the Internet to did not anticipate such real-time data transmission requirements. As such, these new applications have serious technical hurdles to overcome in order to become viable.
Products which place real-time demands on the Internet will be aided by the introduction of an updated hardware interconnection configuration, or "backbone," which provides wider bandwidth transmission capabilities. For instance, the MCI backbone was recently upgraded to 622 megabytes per second. Regardless of such increased bandwidth, the interconnection configuration is comprised of various routers which may still not be fast enough, and can therefore significantly degrade the overall end-to-end performance of the traffic on the Internet. Moreover, even with a bandwidth capability of 622 megabytes per second, the Internet backbone can maximally carry only the following amounts of data: 414--1.5 mbs data streams; 4,859--128 kbs data streams; 21597--28.8 kbs data streams; or combinations thereof. While this is anticipated has being sufficient by various Internet providers, it will quickly prove to be inadequate for near-future applications.
Internal networks, or Intranet sites, might also be used for data transfer and utilize the same technology as the Internet. Intranets, however, are privately owned and operated and are not accessible by the general public. Message and data traffic in such private networks is generally much lower than more crowded public networks. Intranets are typically much more expensive for connect time, and therefore any related increase in throughput comes at a significantly higher price to the user.
To maximize accessibility of certain data, broadcasts of radio shows, sporting events, and the like are currently provided via Internet connections whereby the broadcast is accessible through a specific web page connection. However, as detailed above, each web page connection requires a high throughput two-way connection through the standard Internet architecture. A given Internet backbone will be quickly overburdened with users if the entire set of potential broadcasters across world began to provide broadcast services via such web page connections. Such broadcast methods through the Internet thereby prove to be ineffective given the two-way data throughput needed to access web pages and real-time data.
Furthermore, broadcasts are typically funded and driven by advertising concerns. A broadcast provided through a centralized location, such as a web page for real-time Internet connection, will be limited by a practicality to offer only nationally advertised products, such as Coke or Pepsi. Since people might be connected to this web page from around the world, local merchants would have little incentive to pay to advertise to distant customers outside of their marketing area. Local merchants, instead, would want to inject their local advertising into the data transmission or broadcasts in such a way not currently available the Internet.
There is an enormous demand for the delivery of large amounts of content to a large number of listeners. The broadcast channels of today, such as radio and TV, can only deliver a small number of channels to a large number of listeners. Their delivery mechanism is well known to customers. The broadcaster transmits programs and the listener must "tune in" at the proper time and channel to receive the desired show.
"On Demand" systems have been attempted by the cable industry. Such systems attempt to transport the program or show from a central repository (server) to the user (client) in response to his/her request. To initiate the request, the user selects from a list of candidate programs and requests that the system deliver the selected program.
The foregoing "on demand" model of content delivery places two significant requirements on the delivery system. First, there should be a direct connection between each content storage device (server) and each listener (client). The phone system is an example of such a point-to-point interconnection system. Another example of such an interconnection system is the Internet, which is also largely based on the terrestrial telecommunications networks. Second, the server must be capable of delivering all the programs to the requesting clients at the time that which the client demands the programming.
The foregoing requirements can be met using the Internet. However, as will become evident, the Internet is not suitable for any type of high bandwidth on-demand system. In today's Internet, all the users share a terrestrial infrastructure and, as a result, the total throughput is limited. In other words, the Internet is a party line shared by a large number of users and each subscriber must wait for the line to be free before he/she can send data. Since the signal from the server is generally a high bandwidth signal including multimedia content, any degradation of the throughput from the server to the clients results in an annoying disruption of the video and/or audio at the clients. Successful transmission of real-time streaming multimedia content requires sufficient transmission bandwidth between the server and the client. Since standard IP transmission facilities are a party line, attempts have been made to impose a quality of service (QOS) into this transmission structure. This QOS feature is accomplished by the new bandwidth reservation protocol called RSVP. This new protocol must be active in each network element along the path from the client to the server for it to be effective. Until RSVP is fully enabled, QOS cannot be guaranteed.
Once RSVP is fully deployed, then the mechanical process of reserving bandwidth will be possible. The next limitation encountered will be the problem of limited transmission bandwidth. Consider the case where the sum of all bandwidth reservations exceeds available transmission bandwidth. To reduce the excessive use of bandwidth reservation, transmission providers anticipate transmission charges based on the amount of bandwidth reserved. This bandwidth charge is not in the spirit of today's free connectivity.
Another example of the limitations inherent in the finite throughput of the Internet is the generally limited audience size for a given transmission link. For example, if there is a 622 megabit/second (mbs) link from an Internet server in New York to a number of clients in Los Angeles and each client requires a separate 28.8 kilobit/sec (kbs) connection to the server, then this link can only support about 22,000 clients, a relatively small number of clients when compared to the cost of a server capable of supplying the 622 mbs data content. The costs further escalate and the client audience size capability further diminishes as each client connects to the server using higher bandwidth modems or the like. Still further, the same large demand is placed on the server if each of the 22,000 clients requests the same program but at different times or if each of the clients request a different program at the same, or nearly the same time. The large bandwidth requirements (622 mbs) to supply a relatively small number of clients (22,000) coupled with the stringent requirements placed on the server to supply the content to each client has created problems that "on-demand" systems have yet to economically overcome.
A new development in the LAN/WAN technology is called "multicasting." Multicasting in LAN/WAN parlance means that only one copy of a signal is used until the last possible moment. For example, if a server in New York wants to deliver the same data to someone in Kansas City, Dallas, San Francisco, and Los Angeles, then only one signal needs to be sent to Kansas City. There it would be replicated and sent separately to San Francisco, Los Angeles, and Dallas. Thus the transmission costs and bandwidth used by the transmission would be minimized and the server in New York would only have to send one copy of the signal to Kansas City. This scenario is illustrated in FIG. 1A.
Multicasting helps to somewhat mitigate the transmission costs but there are still a great number of cases where it provides little optimization. For example, if there is one person in each city in the U.S. that wants to view the same program generated by the server in New York, then the server must send the signal to all those cities, effectively multiplying the amount of bandwidth used on the network. As such, the transmission is still expensive. Further, the multicast system model breaks down at high bandwidths and during periods of low data throughput within the Internet infrastructure, resulting in annoying degradation of the transmission content.
Another issue is distribution of information between autonomous systems. This is called peering. FIG. 1B shows three autonomous simple systems labeled AS0, AS1 and AS2. These autonomous systems are self contained networks consisting of host computers (clients and servers) interconnected by transmission facilities. Each autonomous system is connected to other autonomous systems by peering links. These are shown in FIG. 1B by the transmission facilities labeled PL01, PL02 and PL12.
Peering allows a host in one autonomous system to communicate with a host in a different autonomous system. This requires that the routers at the end of the peering links know how to route traffic from one system to the other. Special routing protocols, such as boundary gateway protocol, enable the interconnection of autonomous systems.
Assume that host H1 in AS0 wants to communicate with host H2 in AS1 and H3 in AS2. To do this, H1 communicates with PL01 to reach H2 and PL02 to reach H3. If host H1 wants to multicast a message to multiple hosts in each of the autonomous systems, then boundary routers involved must understand the multicast protocols.
Backbone providers that form each of autonomous systems are reluctant to enable multicast over their peering links because of the unknown load placed on boundary routers and billing issues related to this new traffic which originates outside of their autonomous systems.
The present inventors have recognized that a different approach must be taken to provide a large amount of content to a large number of listeners. The proposed system proposes that the "on-demand" model and point-to-point connection model both be abandoned. In their place, the "broadcast" model is combined with localized multicast connections that selectively allow a client to receive the high bandwidth content of the broadcast.
The broadcast model assumes that the server delivers specific content at specific times on a specific channel as is currently done in today's radio and television industry. "Near on demand" can be affected by playing the same content at staggered times on different transmission channels, preferably, dedicated satellite broadcast channels. Localized receivers receive the broadcast channels and convey the content over a network using a mutlicast protocol that allows any client on the network to selectively access the broadcast content from the single broadcast. This single broadcast provides, in effect, an overlay network that bypasses congestion and other problems in the existing Internet infrastructure.
FIG. 1C shows how host H1 multicast directly to H2 and H3 via satellite or another dedicated link separate from the backbone of the Internet. This type of interconnection bypasses the peering links and the resulting congestion and billing issues. The present invention is based on the recognition of this advantage of using a separate dedicated link and implements the resulting solution in a unique manner.
Accordingly, what is needed is a data transmission system which is capable of sending multiple channels of broadcast data, or multicasting, to receiving computers without being injured by the bandwidth and car were constraints of to-way Internet connections. The ability to interconnects local programming and/or advertising into received broadcast transmissions should also be included. Data channels should therefore be configured, compressed, and encoded for transmission via satellite, or transmission via the existing Internet. Routers at the receiving end should be capable of replicating any downlinked broadcast signals. The local server would thereby provide the replicated transmission to any of the requesting users through a modem server, with local programming and/or advertising interspersed into the broadcast. Hence, users might receive the real-time broadcast transmission through a personal computer without having to establish an individual two-way connection to a Internet web page or real-time Internet connection.